Contact grids are used in many applications where it is necessary to provide efficient exchange between a liquid and a gaseous fluid. One common use is the incorporation of such grids in layer as packing for scrubbing, cooling or distillation towers. In all of these systems, the basic design criteria are the same; the surfaces of the grid should retard the descent of the liquid, create vapor turbulence, and provide additional surface area for gas-liquid contact. At the same time contact grid designs must avoid large pressure drops across the packing and prevent adverse back pressure effects upstream.
Certain prior act contact grids are described in U.S. Pat. No. 3,343,821 issued on Sept. 26, 1967. U.S. Pat. No. 3,343,821 discloses elongated grid members having formations which jut out from the members and, thus, restrict vapor passage therebetween.
One disadvantage of some prior art contact grids has been the complexity and cost associated with the manufacture of the grid elements and contact grids as well as the difficulties encountered in fabricating such contact grids. U.S. Pat. No. 3,343,821 discloses grid members having integral diagonal cross-bars formed by the cutting and bending of the grid members, and describes how such cross-bars may be welded together to form a grid. When grids are so constructed, care must be taken to insure that the grid members are properly cut and bent, and that the welds are clean. Furthermore, it should be apparent that the joints formed by this method have less than optimal mechanical strength insofar as they are free-standing welds.
Prior art contact grids also suffer from a deficiency of drip points or other means to generate small drops of liquid. While contact grids are known to create vapor turbulence and provide additional contact area on their surfaces, the prior art structures are not designed to maximize the number of small drops of liquid, whereby gas-liquid exchange can occur all along the nearly spherical surfaces of the drops.
Therefore, there exists a need for a more efficient, simplified gas-liquid contact grid, which is inexpensive to manufacture and easy to construct. Additionally, there is a need to improve the mechanical strength of grid structures without reliance on expensive, high grade materials.